According to 3GPP (Third Generation Partnership Project), at the present time, a radio communication system employing LTE (Long Term Evolution) and the like, the standardization of which is under progress, requires both an S1 connection which is a logical transmission path between a radio base station (hereinafter, referred to as an “LTE base station”) and a core network and an X2 connection which is a logical transmission path among radio base stations in order to achieve a quick handover, reduction of a processing load in the core network, and the like.
In order to establish the X2 connection, the LTE base station acquires information on other neighboring LTE base stations and holds a neighboring base station list (hereinafter, referred to as a “neighbor list”) as a list of information on the other LTE base stations. The other neighboring LTE base stations indicate other LTE base stations located at a close distance from the LTE base station. The LTE base station holds the neighbor list, so that it is possible to achieve the establishment of the X2 connection, load distribution among the LTE base stations, and control of restriction and the like at the time of maintenance.
As a technique in which the LTE base station acquires the neighbor list, employing ANR (Automatic Neighbour Relation Function) is considered. According to the ANR, the LTE base station receives a measurement report, which is periodically transmitted from a radio terminal or which is transmitted at every time of an event, and obtains the neighbor list based on the measurement report (for example, refer to Non Patent Literature 1).
Furthermore, as a method in which the LTE base station selects other LTE base stations that can establish the X2 connection, based on the neighbor list obtained by the ANR, there is proposed a technique of updating a White List and a Black List as the neighbor list based on OAM (Operation and Maintenance) information. Here, the White List is a list including information on other LTE base stations, which are partners to which the X2 connection is to be actively established, and the Black List is a list including information on other LTE base stations that cannot establish the X2 connection.
Furthermore, as a technique in which the LTE base station performs ICIC (Inter-Cell Interference Coordination), a technique based on an LI (Load Information) message exchanged among LTE base stations is defined. The LI message includes OI (Overload Indicator), HII (High Interference Indicator), and RNTP (Relative Narrowband Tx Power) as interference control information for reducing interference.